Frame structure for support of large delay spread deployment scenarios

ABSTRACT

A frame structure for support of large delay spread deployment scenarios (e.g., cellular system operation in large cell sizes or low frequency bands) is generally presented. In this regard a method is introduced comprising partitioning a radio frame into a plurality of equal-sized (or non-equal-sized) sub-frames to simplify system implementation. Other embodiments are also disclosed and claimed.

BACKGROUND OF THE INVENTION

In an orthogonal frequency division multiplexing (OFDMA)-based cellularradio interface, such as described in patent application Ser. No.11/907,808, by Sassan Ahmadi and Hujun Yin, filed on Oct. 12, 2007,which is herein incorporated by reference in its entirety, propagationof radio signals in large cell sizes and/or lower frequency bands canlead to larger delay spread and consequently can cause inter-symbolinterference (ISI) effects in the received signals. In the OFDM-basedsystems, the effects of ISI are mitigated by the cyclic prefix that isadded to the beginning of the OFDM symbols. The larger the delay spread,the longer the cyclic prefix should be used to alleviate the ISIeffects.

BRIEF DESCRIPTION OF THE DRAWING

The subject matter regarded as the invention is particularly pointed outand distinctly claimed in the concluding portion of the specification.The invention, however, both as to organization and method of operation,together with objects, features and advantages thereof, may best beunderstood by reference to the following detailed description when readwith the accompanied drawings in which:

FIG. 1 is a schematic illustration of a wireless network according to anembodiment of the present invention;

FIG. 2 is a schematic illustration of an apparatus for use in a wirelessnetwork according to an embodiment of the present invention;

FIG. 3 is a schematic illustration of a frame structure according to anembodiment of the present invention;

FIG. 4 is a schematic illustration of a super-frame structure accordingto an embodiment of the present invention;

FIG. 5 is a schematic illustration of a super-frame structure accordingto an embodiment of the present invention;

FIGS. 6, 6A, and 6B are schematic illustrations of super-frame structureaccording to an embodiment of the present invention;

FIG. 7 is a schematic illustration of a super-frame structure having anew preamble multiplexed with a legacy preamble according to anembodiment of the present invention;

FIG. 8 is a schematic illustration of a super-frame structure having asupplemental preamble multiplexed with a legacy preamble, where the newpreamble may be obscured from legacy terminals, according to anembodiment of the present invention;

FIG. 9 is a schematic illustration of a frame structure partitioned inthe time and/or frequency domain according to an embodiment of thepresent invention;

FIG. 10 is a schematic illustration of a frame structure in FDD duplexmode according to an embodiment of the present invention;

FIGS. 11-13 are schematic illustrations of frame structures, accordingto embodiments of the present invention;

FIG. 14 is a table of OFDMA parameters according to embodiments of thepresent invention; and

FIG. 15 is a flow chart of a method according to an embodiment of thepresent invention.

It will be appreciated that for simplicity and clarity of illustration,elements shown in the drawings have not necessarily been drawnaccurately or to scale. For example, the dimensions of some of theelements may be exaggerated relative to other elements for clarity orseveral physical components included in one functional block or element.Further, where considered appropriate, reference numerals may berepeated among the drawings to indicate corresponding or analogouselements. Moreover, some of the blocks depicted in the drawings may becombined into a single function.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of the invention.However it will be understood by those skilled in the art that thepresent invention may be practiced without these specific details. Inother instances, well-known methods, procedures, components and circuitshave not been described in detail so as not to obscure the presentinvention.

Unless specifically stated otherwise, as apparent from the followingdiscussions, it is appreciated that throughout the specificationdiscussions utilizing terms such as “processing,” “computing,”“calculating,” “determining,” or the like, refer to the action and/orprocesses of a computer or computing system, or similar electroniccomputing device, that manipulate and/or transform data represented asphysical, such as electronic, quantities within the computing system'sregisters and/or memories into other data similarly represented asphysical quantities within the computing system's memories, registers orother such information storage, transmission or display devices. Inaddition, the term “plurality” may be used throughout the specificationto describe two or more components, devices, elements, parameters andthe like.

While the following detailed description may describe variousembodiments of the present invention in relation to wireless networksutilizing orthogonal frequency division multiplexing (OFDM) modulation,the embodiments of present invention are not limited thereto and, forexample, may be implemented using other modulation and/or coding schemeswhere suitably applicable. Further, while example embodiments aredescribed herein in relation to wireless metropolitan area networks(WMANs), the invention is not limited thereto and can be applied toother types of wireless networks where similar advantages may beobtained. Such networks specifically include, but are not limited to,wireless local area networks (WLANs), wireless personal area networks(WPANs), and/or wireless wide area networks (WWANs).

The following inventive embodiments may be used in a variety ofapplications including transmitters and receivers of a radio system,although the present invention is not limited in this respect. Radiosystems specifically included within the scope of the present inventioninclude, but are not limited to, network interface cards (NICs), networkadaptors, mobile stations, base stations, access points (APs), gateways,bridges, hubs and cellular radiotelephones. Further, the radio systemswithin the scope of the invention may include cellular radiotelephonesystems, satellite systems, personal communication systems (PCS),two-way radio systems, two-way pagers, personal computers (PCs) andrelated peripherals, personal digital assistants (PDAs), personalcomputing accessories and all existing and future arising systems whichmay be related in nature and to which the principles of the inventiveembodiments could be suitably applied.

Reference is made to FIG. 1, which schematically illustrates a wirelessnetwork 100 according to an embodiment of the present invention.Wireless network 100 may include provider network (PN) 120, a basestation (BS) 118, and one or more subscriber or other stations 110, 112,114, and/or 116, which may be for example mobile or fixed subscriberstations. In some embodiments, base station 118, for example, in WLANs,may be referred to as an access point (AP), terminal, and/or node, andsubscriber stations 110, 112, 114, and/or 116 may be referred to as astation (STA), terminal, and/or node. However, the terms base stationand subscriber station are used merely as an example throughout thisspecification and their denotation in this respect is in no way intendedto limit the inventive embodiments to any particular type of network orprotocols.

Wireless network 100 may facilitate wireless access between each ofsubscriber stations 110, 112, 114, and/or 116 and PN 120. For example,wireless network 100 may be configured to use one or more protocolsspecified in by the Institute of Electrical and Electronics Engineers(IEEE) 802.11™ standards (“IEEE Standard for Wireless LAN Medium AccessControl (MAC) and Physical Layer (PHY) Specification. 1999 Edition”,reaffirmed Jun. 12, 2003), such as IEEE 802.11a™-1999; IEEE802.11b™-1999/Cor1-2001; IEEE 802.11g™-2003; and/or IEEE 802.11n™, inthe IEEE 802.16™ standards (“IEEE Standard for Local and MetropolitanArea Networks—Part 16: Air Interface for Fixed Broadband Wireless AccessSystem”, Oct. 1, 2004), such as IEEE 802.16-2004/Cor1-2005 or IEEE Std802.16-2009, which may herein be referred to as the “IEEE Std802.16-2009” or “WiMAX” standards, and/or in the IEEE 802.15.1™standards (“IEEE Standard for Local and Metropolitan AreaNetworks—Specific Requirements. Part 15.1: Wireless Medium AccessControl (MAC) and Physical Layer (PHY) Specifications for WirelessPersonal Area Networks (WPANs™)”, Jun. 14, 2005), although the inventionis not limited in this respect and other standards may be used. In someembodiments, attributes, compatibility, and/or functionality of wirelessnetwork 100 and components thereof may be defined according to, forexample, the IEEE 802.16 standards (e.g., which may be referred to as aworldwide interoperability for microwave access (WiMAX)). Alternativelyor in addition, wireless network 100 may use devices and/or protocolsthat may be compatible with a 3^(rd) Generation Partnership Project(3GPP) Long Term Evolution (LTE) cellular network or any protocols forWPANs or WWANs.

Embodiments of the invention may enable the next generation of mobileWiMAX systems (e.g., based on IEEE 802.16m standard) to efficientlysupport substantially high mobility and low latency applications, suchas, for example, Voice-over-Internet Protocol (VoIP), interactive gamingover the air-interface, deployment in larger cell-sizes or lowerfrequency bands, and/or “multi-hop” relay operations, while enablingbackward compatible operations and integration with reference standards(e.g., the legacy mobile WiMAX systems based on IEEE Std 802.16-2009).

In some embodiments, base station 118 may manage and/or control wirelesscommunications among subscriber stations 110, 112, 114, and/or 116 andbetween subscriber stations 110, 112, 114, and/or 116 and providernetwork 120. Subscriber stations 110, 112, 114, and/or 116 may, in turn,facilitate various service connections of other devices (not shown) towireless network 100 via a private or public local area network (LAN),although the embodiments are not limited in this respect.

Reference is made to FIG. 2, which schematically illustrates anapparatus 130 for use in a wireless network according to an embodimentof the invention. For example, apparatus 130 may be a terminal, device,or node (e.g., one of subscriber stations 110, 112, 114, and/or 116,base station 118, and/or provider network 120, described in FIG. 1) forcommunicating with other terminals, devices, or nodes, in a wirelessnetwork (e.g., wireless network 100, described in FIG. 1). Apparatus 130may include a controller or processing circuit 150 including logic(e.g., including hard circuitry, processor and software, or acombination thereof) to determine the false frame detection rate and/oradjust the sensitivity of frame detection as described in one or moreembodiments of the invention. In some embodiments, apparatus 130 mayinclude a radio frequency (RF) interface 140 and/or a medium accesscontroller (MAC)/baseband processor circuit 150.

In one embodiment, RF interface 140 may include a component orcombination of components adapted for transmitting and/or receivingsingle carrier or multi-carrier modulated signals (e.g., includingcomplementary code keying (CCK) and/or orthogonal frequency divisionmultiplexing (OFDM) symbols) although the inventive embodiments are notlimited to any specific over-the-air interface or modulation scheme. RFinterface 140 may include, for example, a receiver 142, a transmitter144 and/or a frequency synthesizer 146. Interface 140 may include biascontrols, a crystal oscillator and/or one or more antennas 148 and/or149. In another embodiment, RF interface 140 may use externalvoltage-controlled oscillators (VCOs), surface acoustic wave filters,intermediate frequency (IF) filters and/or RF filters, as desired. Dueto the variety of potential RF interface designs an expansivedescription thereof is omitted.

Processing circuit 150 may communicate with RF interface 140 to processreceive and/or transmit signals and may include, for example, ananalog-to-digital converter 152 for down converting received signals, adigital-to-analog converter 154 for up converting signals fortransmission. Further, processor circuit 150 may include a baseband orphysical layer (PHY) processing circuit 156 for PHY link layerprocessing of respective receive/transmit signals. Processing circuit150 may include, for example, a processing circuit 159 for medium accesscontrol (MAC)/data link layer processing. Processing circuit 150 mayinclude a memory controller 158 for communicating with processingcircuit 159 and/or a base station management entity 160, for example,via interfaces 155.

In some embodiments of the present invention, PHY processing circuit 156may include a frame construction and/or detection module, in combinationwith additional circuitry such as a buffer memory, to construct and/ordeconstruct super-frames as in the embodiments previously described.Alternatively or in addition, MAC processing circuit 159 may shareprocessing for certain of these functions or perform these processesindependent of PHY processing circuit 156. In some embodiments, MAC andPHY processing may be integrated into a single circuit if desired.

Apparatus 130 may be, for example, a base station, an access point, asubscriber station, a device, a terminal, a node, a hybrid coordinator,a wireless router, a NIC and/or network adaptor for computing devices, amobile station or other device suitable to implement the inventivemethods, protocols and/or architectures described herein. Accordingly,functions and/or specific configurations of apparatus 130 describedherein, may be included or omitted in various embodiments of apparatus130, as suitably desired. In some embodiments, apparatus 130 may beconfigured to be compatible with protocols and frequencies associatedone or more of the IEEE 802.11, 802.15 and/or 802.16 standards forWLANs, WPANs and/or broadband wireless networks, cited herein, althoughthe embodiments are not limited in this respect.

Embodiments of apparatus 130 may be implemented using single inputsingle output (SISO) architectures. However, as shown in FIG. 2, certainimplementations may include multiple antennas (e.g., antennas 148 and149) for transmission and/or reception using adaptive antenna techniquesfor beamforming or spatial division multiple access (SDMA) and/or usingmultiple input multiple output (MIMO) communication techniques.

The components and features of station 130 may be implemented using anycombination of discrete circuitry, application specific integratedcircuits (ASICs), logic gates and/or single chip architectures. Further,the features of apparatus 130 may be implemented using microcontrollers,programmable logic arrays and/or microprocessors or any combination ofthe foregoing where suitably appropriate. It is noted that hardware,firmware and/or software elements may be collectively or individuallyreferred to herein as “logic” or “circuit.”

It should be appreciated that the example apparatus 130 shown in theblock diagram of FIG. 2 may represent one functionally descriptiveexample of many potential implementations. Accordingly, division,omission or inclusion of block functions depicted in the accompanyingfigures does not infer that the hardware components, circuits, softwareand/or elements for implementing these functions would be necessarily bedivided, omitted, or included in embodiments of the present invention.

Reference is made to FIG. 3, which schematically illustrates a frame 300structure according to an embodiment of the present invention. Frame 300(e.g., a radio frame) may be a portion of a transmitted and/or receivedcommunication in, for example, wireless network 100. In someembodiments, frame 300 may describe a periodically repeating segmentstructure of a larger communication signal or stream. In someembodiments, repeating frame 300 may include substantially differentinformation, for example, during substantially each separatetransmission. Frame 300 may be defined and may include broadbandwireless access technology according to, for example, the IEEE Std802.16-2009 or mobile WiMAX profiles. According to the mobile WiMAXprofiles, the duration of frame 300 or transmission time interval (TTI)may be, for example, approximately 5 ms. Other frame or radio framesizes such as for example 2, 2.5, 4, 8, 10, 12, and 20 ms may be used asfor example specified in the IEEE Std 802.16-2009 specification.

In some embodiments, frame 300 may be transmitted and/or received, forexample, according to a time division duplex (TDD) mode or scheme. Othertime and/or frequency schemes may be used (e.g., such as a frequencydivision duplex (FDD) mode or scheme) according to embodiments of theinvention.

Frame 300 may include an integer number of OFDM symbols or othermultiplexing symbols. The number of OFDM symbols per frame may bedetermined, for example, according to a choice of OFDM numerology (e.g.,sub-carrier spacing, cyclic prefix length, sampling frequency, etc.). Insome embodiments, OFDM numerologies may be determined, set, or obtained,for example, depending, on a bandwidth and sampling frequency (e.g., oran over-sampling factor according to the mobile WiMAX profiles). Invarious embodiments, substantially different OFDM numerologies may beused, which may result in substantially different number of OFDM symbolsin frame 300.

In some embodiments, frame 300 may include idle symbols and/or idle timeslots. In one embodiment, frame 300 may include one or more switchingperiods 302 and/or 304, for example, for changing between apre-designated downlink (DL) transmission 306 and a pre-designateduplink (UL) transmission 308 when a TDD duplex mode or scheme is used.In other embodiments, for example, when an FDD duplex scheme is used,since DL transmissions 306 and UL transmissions 308 may be sentsubstantially at the same or overlapping times (e.g., over differentfrequencies or network channels) frame 300 may include substantially fewor no idle symbols, idle time slots, and/or switching periods 302 and/or304.

In some embodiments, the TTI or the duration of frame 300 may be, forexample, approximately 5 ms. A round trip time (RTT) (e.g., the timeinterval between two consecutive pre-scheduled DL transmissions 306 to aspecific wireless node may be, for example, approximately 10 ms.Wireless networks (e.g., wireless network 100) having rapidly changingchannel conditions and/or small coherence times (e.g., rapidly movingmobile stations or nodes, such as automobiles having vehicular speedsof, for example, in the excess of approximately 120 kilometers per hour(km/h)) may use mechanisms for supporting substantially high mobility invarying channel conditions. Embodiments of the invention may supportwireless network 100 having substantially small round trip times, forexample, to enable substantially fast-varying channel condition feedbackbetween subscriber stations 110, 112, 114, and/or 116, such as a mobilestation, and base station 118. Other time durations may be used.

The current IEEE Std 802.16-2009 specification standard frame structuremay include restrictions, such as substantially long TTIs that aretypically not suitable for supporting substantially fast feedback andlow access latency (e.g., less than 10 ms), which may be used by, forexample, emerging radio access technologies.

Embodiments of the present invention may include or use a modifiedversion of the frame 300 structure for supporting lower latencyoperations, while maintaining backward compatibility, for example, tothe IEEE Std 802.16-2009 specification frame structure. Frame 300structure may be used, for example, in the next generation of mobileWiMAX systems and devices (e.g., including the IEEE 802.16m standard).In some embodiments, frame 300 structure or portions thereof may betransparent to the legacy terminals (e.g., which operate according tomobile WiMAX profiles and IEEE Std 802.16-2009) and may be used only forcommunication between BSs, subscriber stations, and/or MSs that bothoperate based on the IEEE 802.16m standard.

According to embodiments of the invention, wireless network 100 andcomponents thereof, which may communicate using the new frame structure(e.g., described according to FIGS. 3-15), may be backward compatiblewith a reference network, which may communicate using a legacy framestructure (e.g., described according to the mobile WiMAX profiles andbased on the IEEE Std 802.16-2009). In some embodiments, backwardcompatibility may include for example, that a legacy terminal (e.g.,which may communicate using legacy and/or reference frame structures)may operate in a wireless network with no significant impact on theperformance and operation of the terminal relative to a legacy network.In some embodiments, a new (e.g., a non-legacy) terminal or subscriberstation using the new (e.g., a non-legacy) frame structure may operatein a legacy network with no significant impact on the performance andoperation of the terminal relative to the wireless network. For example,the new terminal may be “backward compatible”. In some embodiments,wireless network 100 may support both legacy and new (e.g., anon-legacy) terminals, for example, at substantially the same time(e.g., where time division multiplexing of the new and legacy framesoverlap in the same frame). In some embodiments, wireless network 100may enable seamless communication, mobility, and handoff between legacyterminals and new terminals. When used herein, “new”, “evolved” or“updated,” and “next generation” are merely relative to “old”, “legacy”or “current”, etc. For example, a “new” standard may be a standard thatis in use as of the date of the filing of this application, and a“legacy” system may be one that is in use both prior to the date offiling this application and for some time after the filing of thisapplication; a “new” system is one implemented or developed after a“legacy” system, typically including improvements and updates. “New”,“evolved”, “updated”, etc. systems are often backward compatible suchthat they are usable with “old”, “legacy” or prior systems or standards.

According to embodiments of the invention, the new frame structure mayinclude new synchronization and broadcast channels to extend thecapabilities of the IEEE Std 802.16-2009 by, for example, enhancingsystem acquisition and/or enhancing cell selection at low signal tointerference+noise ratios (SINR). According to the IEEE Std 802.16-2009a broadcast channel (e.g., and a DL channel descriptor and UL channeldescriptor) are typically not located at a pre-defined location in aframe, the mobile stations have to decode the common control channel(e.g., MAP) for acquiring system configuration information.

According to an embodiment of the present invention, the new framestructure may include for example a super-frame that includes an integernumber of radio frames, which may include synchronization and/orbroadcast information and/or messages, such as, system configurationinformation, which may simplify wireless network 100 operations andfurther reduce the overhead and acquisition latency of wireless network100.

Reference is made to FIG. 4, which schematically illustrates asuper-frame 400 structure according to an embodiment of the presentinvention. In some embodiments, a transmission between terminals ornodes may include, for example, one or more super-frames 400.Super-frame 400 may include or be partitioned into a fixed and/orpre-determined number of frames 410. In other embodiments, the number offrames 410 in each of two or more of super-frames 400 may be different.The number of frames, M, 410 within a super-frame 400 (e.g., M, may bean integer, where M=2, 3, 4 . . .) may be a design parameter and may bespecified in a standard specification and, for example, may be fixed fora particular profile and deployment. In some embodiments, the number offrames 410 within super-frame 400 may be determined by one or morefactors, including but not limited to, for example, target systemacquisition time, a maximum permissible distance between two consecutivepreambles (e.g., synchronization channels), the minimum number ofpreambles that may be averaged during system acquisition for thedetection of the preamble, and/or a maximum permissible distance betweentwo consecutive broadcast channels (e.g., system configurationinformation or paging channels).

In one embodiment, substantially each super-frame 400 may be partitionedinto or include two or more (e.g., four (4)) frames 410. Other numbersof partitions, divisions, or frames may be used. The length of eachframe 410 may be for example approximately 5 ms, for example, forestablishing backward compatibility with systems compliant with IEEE Std802.16-2009. Other frame or radio frame lengths may be used. Each offrames 410 may be further partitioned or sub-divided into two or more(e.g., eight (8)) sub-frames 420. Other numbers of divisions may beused. The length of sub-frame 420 may determine the TTI for terminalsthat may be compliant with the new standard and, for example,incorporate super-frame 400 and/or frame 410 structures. The beginningand end of each of the TTIs may be substantially aligned or synchronizedwith, for example, a sub-frame boundary. Each TTI may contain an integernumber of sub-frames (e.g. typically one or two sub-frames). Eachsub-frame 420 may be partitioned into or include a fixed number of OFDMsymbols 430. In one embodiment, each sub-frame 420 may be partitionedinto or include, for example, six (6) OFDM symbols, so that the numberof OFDM symbols 430 within a sub-frame (e.g., the length of sub-frame420) may be compatible to resource block sizes (e.g., sub-channels)corresponding to various permutation schemes, for example, specified inthe IEEE Std 802.16-2009.

In other embodiments, there may be other or alternative numbers,lengths, sizes, and/or variations, of super-frames 400, frames 410,sub-frames 420, and/or OFDM symbols 430. The numbers used herein arepresented for demonstrative purposes only. In another embodiment, thelength of frames 410 (e.g., approximately 5 ms) and the number of OFDMsymbols 430 (e.g., six (6)), may be set for establishing backwardcompatibility with IEEE Std 802.16-2009 compliant systems, devices,and/or transmissions.

Permutation schemes, for example, defined according to current standardspecifications, may include a number, for example, from one to six,slots for transmitting signals and/or resource blocks. The boundary ofphysical a resource block may, for example, be aligned with a sub-frameboundary. In some embodiments, each physical resource block may besubstantially contained within a single sub-frame 420. In otherembodiments, each physical resource block may be substantially containedwithin two consecutive sub-frames.

It may be appreciated by those skilled in the art that embodiments ofthe invention, for example, including, super-frame 400 structures, maybe applied using either of the TDD and FDD duplexing schemes or modes.In the FDD duplex mode, each of the DL and UL transmissions may becommunicated, for example, concurrently, on respective frequencies orchannels. In the TDD duplex mode, each of the DL and UL transmissionsmay be communicated, for example, at substantially non-overlappingintervals (e.g., according to time division multiplexing (TDM) scheme)over substantially the same frequency or channel. In the TDD duplex modeof operation and within any frame 410, sub-frames 420 may be configuredto DL and UL transmissions (e.g., DL transmission 306 and ULtransmission 308) for example statically in each deployment. The DL andUL transmissions may be separated by idle times and/or idle symbols forswitching between DL and UL transmissions (e.g., during switchingperiods 302 and/or 304).

In one embodiment of the invention, “legacy zones” and “new zones” mayinclude periods, portions or zones, for example, of DL or ULtransmission, specifically designed to substantially only communicatewith legacy terminals or new terminals, respectively. In the TDD duplexmode of the IEEE Std 802.16-2009, each of DL transmission 306 and ULtransmission 308 may be further partitioned into two or more permutationzones. In some embodiments, the number of contiguous OFDM or othersymbols 430 in a frame 410, may be referred to as, for example, apermutation zone (e.g., permutation zone 310, described in reference toFIG. 3). The permutation zone may, for example, include a number ofcontiguous OFDM symbols (e.g., in DL and UL transmissions 306 and 308,described in reference to FIG. 3) that use substantially the samepermutation (e.g., partially used sub-channel (PUSC) to distributedallocation of sub-carriers, Adaptive Modulation and Coding (AMC) forlocalized allocation of sub-carriers, etc.).

According to an embodiment of the invention, a frame may include or maybe partitioned into legacy zones and new zones (other terms may beused). In one embodiment, legacy terminals and new terminals maycommunicate using legacy zones and new zones, respectively. In someembodiments, new terminals may communicate using both legacy zones andnew zones. Legacy terminals typically only communicate using legacyzones. In one embodiment, in the frame, each of DL transmissions may befurther partitioned into two or more zones, for example, including a DLtransmission legacy zones and a DL transmission new (e.g., non-legacy)zones and each of UL transmissions may be further partitioned into twoor more zones, for example, including UL transmission legacy zones andUL transmission new (e.g., non-legacy) zones.

Embodiments of the invention may provide a partitioning of frames intosub-frames (e.g., where the boundaries of transmission blocks or zonesmay be synchronized with the sub-frame boundaries). According to theIEEE Std 802.16-2009, the boundaries of transmission blocks or zones maystart and end at any OFDM symbol within the boundary of a frame.According to embodiments of the invention, the new zones may use a newand more efficient resource allocation and feedback mechanism. The totalnumber of OFDM symbols within a frame may vary depending on the OFDMnumerology. In order to maintain backward compatibility with the legacymobile WiMAX systems, the same frame size and OFDMA numerology (e.g., orOFDMA parameters) may be used for the IEEE 802.16m systems and thelegacy mobile WiMAX systems. It may be appreciated by those skilled inthe art that all permissible numerologies and/or frame sizes, forexample, specified by the 802.16e-2005 standard, may be used inaccordance with embodiments of the present invention.

Embodiments of the invention may provide super-frame structures that maybe compatible with legacy standards, such as, the IEEE Std 802.16-2009and/or other standards. For example, the super-frame structure mayinclude or may be compatible with a subset of features, for example, asspecified in the mobile WiMAX profile (e.g., and may be backwardscompatible with the mobile WiMAX profile).

Embodiments of the invention may provide a super-frame structure, whichmay be partitioned into a number of frames that include, for example,one or more, legacy synchronization channel (e.g., a IEEE Std802.16-2009 preamble), new synchronization channels (e.g., a IEEE802.16m preamble), broadcast channel (BCH), medium access protocol(MAPs) or common control channel (CCCH) in the new and legacy zonescorresponding to each frame or an integer number of frames.

Reference is made to FIG. 5, which schematically illustrates asuper-frame 500 structure according to an embodiment of the presentinvention. In one embodiment, super-frame 500 may include a legacypreamble 502, for example, which may be referred to as primarysynchronization channel (PSCH). In some embodiments, super-frame 500 mayinclude an additional or supplemental preamble 504, for example, forimproving system timing acquisition and cell selection for newterminals. Supplemental preamble 504 may, for example, be referred to assecondary synchronization channel (SSCH). The synchronization channelsmay include sequences, which may be used and/or deciphered by both basestations and mobile stations, for example, for acquiring frame timingand/or scheduling.

In some embodiments, new preamble 504 may be effectively or partiallytransparent, unreadable, or undetectable to legacy terminals, whilelegacy preamble 502 may be detectable to both legacy and new terminals.In some embodiments, super-frame 500 may include a broadcast channel(BCH) 506. The broadcast channel may contain information that may forexample include system configuration information, paging, and/or otherbroadcast type information, and may be sent by a base station to allmobile stations in the network and/or surrounding area.

As shown in FIG. 5, supplementary or new preamble 504 (e.g., SSCH) maybe located at a fixed position in new or legacy zones. In one embodimentof the present invention, for example, the new preamble 504 may bepositioned at a fixed offset, which may be referred to as, for example,“SSCH_OFFSET”. The SSCH_OFFSET may be a measure of a location of the newpreamble 504, for example, relative to the location of the legacypreamble, for example, in every frame. In some embodiments, the legacypreamble in mobile WiMAX systems may be located in the first OFDM symbolof every frame (as shown in FIG. 9). The value of SSCH_OFFSET may beincluded and broadcasted as part of the system configurationinformation. In some embodiments, when new preamble 504 is detected by amobile terminal, the SSCH_OFFSET may be used to locate the beginning ofa frame. In one embodiment, when SSCH_OFFSET=0, there may be no legacypreamble 502, which may indicate that the network does not supportlegacy terminals. In some embodiments, a new synchronization channel andthe broadcast channel may span a minimum system bandwidth (BW). In someembodiments, the legacy synchronization channel typically spans theentire system BW, an example of which is shown in FIG. 9. The regionpre-designated for communicating new preamble 504 (e.g., via multiplesub-carriers) may be, for example, transparent and/or ignored by legacyterminals. A scheduler for downlink base station or terminaltransmissions typically does not allocate user/systemtraffic/control/signaling in the region pre-designated for communicatingnew preamble 504.

In another embodiment of the present invention, for example, newpreamble 504 may be located, for example, in the beginning of the newframe where the new frame may be located at a fixed offset relative tothe legacy frame. In one embodiment, the fixed offset may be referred toas, for example, “FRAME_OFFSET”, and may be fixed within the frametiming. In some embodiments, the value of the FRAME_OFFSET may be set bya network operator or administrator (e.g., and not broadcast). The newmobile terminals may detect new preamble 504, which may indicate thebeginning of the new frame and, for example, other information channelsrelative to the beginning of the new frame (e.g., as shown in FIG. 6).For example, the timing or periodicity of BCH 506 may be substantiallyaligned with the timing or periodicity of super-frame 500 transmissions.

In various embodiments, super-frame 500 may have substantially differentstructures, which may be distinguished, for example, based on therelative position of legacy preamble 502 and/or new preamble 504 insuper-frame 500, and/or other features or design considerations for theframe structure (e.g., such as a DL scan latency, physical layeroverhead, and other information). It may be appreciated to those skilledin the art that although three options for the structure of super-frame500, including for example, options I, II, and III, may be described,various other structures and/or variations thereof may be used inaccordance with embodiments of the present invention.

The description that follows may include embodiments that mayindividually or collectively be referred to as Option I. Option I, andother “Options” presented herein are examples only, and arenon-limiting.

In some embodiments, new preamble 504 and/or BCH 506 may be positionedsubstantially at the beginning of each super-frame 500, for example, inthe first frame of each super-frame 500 in a communication stream. Insuch embodiments, legacy preamble 502 and new preamble 504 may beseparately positioned (e.g., spaced or offset along the length ofsuper-frame 500). In such embodiments, the impact or visibility of newpreamble 504 to legacy terminals (e.g., which typically only detectlegacy preamble 502) and operations thereof, such as, systemacquisition, may be minimized. New preamble 504 may be periodicallyrepeated at any desirable frequency, for example, substantially everyframe. BCH 506 may contain system-configuration information, pagingchannels, and/or other broadcast information. In some embodiments, BCH506 may be synchronized with super-frame 500 intervals and may appearevery integer number of super-frames. In some embodiments, new terminalsmay use new preamble 504 (e.g., exclusively or additionally) to improvesystem timing acquisition and fast cell selection. For example, newpreamble 504 may include cell identification (ID) information or codesand may be used for acquisition of frame timing by new terminals. Forexample, a cell ID code may include a concatenated base station group IDcode, base station ID code, a sector ID code, and/or other codes orinformation, for example, to simplify the detection (e.g., execute astructured search) of the cell ID.

According to embodiments of the invention described in reference toOption I, since new preamble 504 may be spaced from legacy preamble 502,new preamble 504 may be minimally detectable by legacy terminals. Insome embodiments, in order to minimize the physical layer overhead(layer 1 overhead), for example, which may be increased by using an OFDMsymbol for transmitting new preamble 504, new preamble 504 may betransmitted, for example, over a limited (e.g., minimal) bandwidth ortime, or by using additional sub-carriers corresponding to the same OFDMsymbol for scheduling user traffic, for example, as shown in FIG. 9.

The description that follows may include embodiments that mayindividually or collectively be referred to as Option II.

Reference is made to FIG. 6, which schematically illustrates asuper-frame 600 structure according to an embodiment of the invention.In some embodiments for TDD duplex mode, super-frame 600 may bepartitioned into, for example, four frames with pre-designated legacyperiods, intervals or zones and new or non-legacy periods, intervals orzones. In one embodiment, legacy frame 610 may be further partitionedinto sub-frames, including, for example, DL transmission legacy zones612 and UL transmission legacy zones 616. The new frame 620 may begin ata fixed offset (e.g., FRAME_OFFSET) relative to the beginning of thelegacy frame. The value of the FRAME_OFFSET may be an integer number ofsub-frames and may be determined based on the ratio of the lengths ortime of the DL to UL transmissions (e.g., in TDD duplex mode). Forexample, when FRAME_OFFSET=T_(offset) and T_(sub-frame) denotes thelength of the sub-frame and T_(f) denotes the frame length the value ofthe minimum and maximum permissible values for T_(offset) may bedetermined as follows:

T_(offset)<αT_(f)

-   -   0≦α≦1: the fraction of frame allocated to DL    -   Example: α=0.625 for DL:UL=5:3

nT _(sub-frame) ≦αT _(f) −T _(offset)1≦n<7

T _(offset) =mT _(sub-frame)0≦m<(Number of DL Sub_Frames)−n

In some embodiments, legacy terminals may communicate using legacyframes 610 and new terminals may communicate using new frames 620 and/orlegacy frames 610.

According to embodiments of the invention, for example, in option III,the beginning of new frames 620 and legacy frames 610 may be offset by afixed value, for example, by a frame offset 622 or an offset interval(e.g., a fixed duration of time and/or number of sub-frames).

The relative positions of new frames 620 and legacy frames 610 accordingto one embodiment are depicted in FIG. 6, for example, in TDD duplexmode. For example, in TDD duplex mode, legacy frame 610 structure maystart with a DL transmission 612 and end with an UL transmission 616.For example, new frame 610 structure may start with a DL transmission614, followed by a UL transmission 618, and end with a DL transmission614.

In some embodiments, each new frame 610 may contain a new preamble(e.g., SSCH), for example, in a sub-frame at the start or beginning offrame 610.

In other embodiments, each super-frame 600 may include a super-frameheader (SFH) 624, for example, in a sub-frame at the start or beginningof super-frame 600. For example, SFH 624 may include a new preamble anda broadcast channel.

For example, K and 6-K, K=1, 2, . . ., 6 may denote the number of OFDMsymbols that are allocated to new preamble and broadcast channel,respectively. The number of OFDM symbols allocated to the new and legacypreambles may be as small as one OFDM symbol per channel. In oneembodiment, the remainder of the OFDM symbols available in the SFH 624sub-frame may be allocated, for example, for user traffic, control,and/or control and signaling information, which may minimize the systemlayerl overhead.

SFH 624 may include a new preamble sequence and the broadcastinformation (e.g., including system configuration information and apaging channel). In some embodiments, legacy frames and new frames mayhave a fixed frame offset 622, which may be configurable by the networkoperator.

In some embodiments of the present invention, the legacy zone and newzone may be offset by a fixed number of sub-frames. The offset value maybe substantially stable or fixed within a practical deployment. Due tothe dynamic nature of network traffic in practice, in some frames, thelegacy zone may be under-utilized while the new zone may be fully loadedor vice versa. In some embodiments, a pointer in a IEEE 802.16m commoncontrol channel may be designed and/or used, for example, to point to orindicate a sub-frame in the legacy zone that may be unused by legacyterminals. For example, when legacy zone and/or new zone partitions arefixed, the resources (e.g., sub-frames) may be dynamically allocatedfrom frame to frame maximize the use of physical resources, which mayotherwise be unused.

The description that follows may include embodiments that mayindividually or collectively be referred to as Option III.

Reference is made to FIG. 7, which schematically illustrates asuper-frame 700 structure having a new preamble 704 multiplexed with alegacy preamble 702, according to an embodiment of the presentinvention. In some embodiments, a new preamble 704 may be multiplexedwith a legacy preamble 702, for example, every M frames (e.g., where Mmay be the number of frames within a super-frame 700). For example, thefirst OFDM symbol of the first frame 710 in super-frame 700 may includenew preamble 704 and the M-1 succeeding frames 710 in super-frame 700may include legacy preamble 702. In some embodiments, a common controlchannel (e.g., including DL and UL MAPS) and/or frame control header(FCH) 708 and a BCH 706 transmission may occur, for example, atsuper-frame 700 and frame 710 intervals, respectively.

The acquisition of legacy preamble 702 (e.g., by legacy terminals) maybreak as a result of interruption in the reception of the periodiclegacy preamble 702. Since new preamble 704 and legacy preamble 702 mayshare physical resources, for example, and may be transmitted atsubstantially the same or overlapping times or locations alongsuper-frame 700, there may typically be no additional physical resourceneeded for including the new preamble 704 into a super-frame 700structure. Additionally, in some embodiments, the position of newpreamble 704 may be fixed within a periodic number (one or more) offrames 710.

In some embodiments, when new preamble 704 and legacy preamble 702 arecode division multiplexed, for example, in substantially the same OFDMsymbol, there is typically no substantial impact on the layerl overhead.In such embodiments, some legacy preambles 702 may be transmitted insuccession and, for example, other legacy preambles 702 may besuperimposed with new preamble 704 (e.g., according to multiplexingscheme discussed herein).

In some embodiments, new preamble 704 may be multiplexed with legacypreamble 702 using, for example, a code division multiplexing (CDM)scheme. A CDM scheme may include code division multiplexing new preamble704 and legacy preamble 702, for example, substantially every M frames710, for example, as shown in FIG. 7.

In one embodiment, new preamble 704 and legacy preamble 702 sequencesmay be superimposed and transmitted (e.g., by a new base station orterminal) every M frames, for example, according to the followingequation:

y_(k)=u_(k)+x_(k)u′_(k) where u_(k), u′_(k), x_(k) may denote the k^(th)primary synchronization sequence, the k^(th) new synchronizationsequence, and the k^(th) spreading function. Other (e.g., linear)combinations may be used.

For example, the spreading function may include a set of robustspreading functions, which may substantially cover the newsynchronization sequences. Other multiplexing schemes or combinationsthereof may be used.

In one embodiment, legacy preamble 702 and new preamble 704 may be, forexample, code division multiplexed every fixed number (e.g., M=1, 2, 3 .. .) frames. In such embodiments, legacy terminals may experience orinclude a small degradation in the energy of the legacy preamble every Mframes. The new terminals may detect and extract new preamble 704 thatmay encroach or may be superimposed on legacy preamble 702. As presentedherein, new preamble may be referred to, for example, as “new preamble”,“new preamble”, “new synchronization channel”, “SSCH” and “secondarysynchronization channel”, a new system, profile, and/or standard, may bereferred to, for example, as an “evolved version” of the referencesystem standard.

Reference is made to FIG. 8, which schematically illustrates asuper-frame 800 structure having a new preamble 804 multiplexed with alegacy preamble 802, where legacy preamble 802 may be obscured fromlegacy terminals, according to an embodiment of the present invention.

In some embodiments, the superposition of new preamble 804 on the legacypreamble 802 may, for example, increase interference levels or, forexample, an interference over thermal 820 (IoT) value. The objective isto find the minimum Signal to Interference+Noise Ratio (SINR) that isrequired for proper detection of the legacy preamble or alternativelythe maximum IoT that can be tolerated by the legacy terminals (thisleads to the maximum power that can be used for the new preamble).

In one embodiment of the present invention, a signal received at thes^(th) sub-carrier, y_(s), may be calculated, for example, as shown inthe equations that follow. In one embodiment, new preamble 804associated with each new base station or relay station may besubstantially different, for example, for enabling a mobile station todistinguish, detect, and/or select, different base stations or relaystations in a network. In some embodiments, since the received power 822of new preamble 804 may be determined, or be directly proportional to,the IoT 820, it may be desirable for the IoT 820 to be maximized, forexample, to the extent that the minimum SINR level would allow thelegacy terminals to correctly detect legacy preambles 802. In someembodiments, an optimization of the IoT 820 value may be performed, forexample, according to the equations that follow:

$y_{s} = {{H_{s,k}u_{k}} + {H_{s,k}\chi_{k}u_{k}^{\prime}} + w_{s} + {\sum\limits_{i \neq k}{H_{s,i}u_{i}}} + {\sum\limits_{l \neq k}{H_{s,l}\chi_{l}u_{l}^{\prime}}}}$${SINR}_{s} = {20\log_{10}\frac{{H_{s,k}u_{k}}}{{{H_{s,k}\chi_{k}u_{k}^{\prime}} + w_{s} + {\sum\limits_{i \neq k}{H_{s,i}u_{i}}} + {\sum\limits_{l \neq k}{H_{s,l}\chi_{l}u_{l}^{\prime}}}}}}$${SINR}_{s} \geq {10\; \log_{10}\frac{{{H_{s,k}u_{k}}}^{2}}{{{H_{s,k}\chi_{k}u_{k}^{\prime}}}^{2} + {w_{s}}^{2} + {{\sum\limits_{i \neq k}{H_{s,i}u_{i}}}}^{2} + {{\sum\limits_{l \neq k}{H_{s,l}\chi_{l}u_{l}^{\prime}}}}^{2}}}$IoT = H_(s, k)χ_(k)u_(k)^(′)²${SINR}_{s\mspace{11mu} \min} = {10\; \log_{10}\frac{{{H_{s,k}u_{k}}}^{2}}{{w_{s}}^{2} + {{\sum\limits_{i \neq k}{H_{s,i}u_{i}}}}^{2} + {{\sum\limits_{l \neq k}{H_{s,l}\chi_{l}u_{l}^{\prime}}}}^{2} + {IoT}_{\max}}}$

where terms may be defined, for example, as follows:

y_(s): Received Signal at sth Sub-Carrier

u_(k): Legacy Preamble Sequence sent by kth BS

H_(s,k): Multi-Path Channel Impulse Response

u′_(k): New Preamble Sequence sent by kth BS

x_(k): kth Spreading Function

w_(s): Received Noise at sth Sub-Carrier

-   -   SINR_(s): Signal to Interference+Noise Ratios for Legacy        Terminals

$\sum\limits_{l \neq k}{H_{s,l}\chi_{l}u_{l}^{\prime}}$

Inter-Cell Interference due to New and Legacy Preambles

Other criteria for the optimization of the IoT value may be used. Insome embodiments, when legacy preambles 702 and 802 are code divisionmultiplexed, transmitting new preamble 704 and 804, respectively, mayhave substantially no or minimal effect on the physical layer overheadof the system in which they are transmitted.

In such embodiments, superimposing new preamble 804 onto legacy preamble802 respectively, may limit the received power 822 of new preamble 704and may potentially interfere with or obscure system acquisitions oflegacy preamble 802 by legacy terminals, for example, due to additionalinterference from new preambles transmitted by neighboring base stationsor relay stations. The effect of additional interference may beminimized, for example, using robust preamble detection algorithms, forexample, having minimal sensitivity to instantaneous degradation in thepreamble power.

It may be appreciated by those skilled in the art that each of threeoptions for embodiments of the structure of a super-frame and/orpartitions thereof, including for example, embodiments described inreference to each of options I, II, and III, may be applied to both TDDand FDD duplex schemes. The size and distribution of the new and legacyzones and their corresponding DL and UL transmissions and/or sub-frames,may depend, for example, on factors including but not limited to thedistribution of the new and legacy terminals, network load andperformance optimizations for new and legacy terminals.

Reference is made to FIG. 10, which schematically illustrates a frame1000 structure in FDD duplex mode according to an embodiment of thepresent invention. Frame 1000 may include sub-frames 1030. In someembodiments, super-frame 1000 may include a legacy preamble 1002, a newpreamble 1004, and a BCH 1006, which may be transmitted every integernumber of super-frame transmissions. In one embodiment, legacy preamble1002, new preamble 1004, and/or BCH 1006 may be positioned at thebeginning of frame 1000. According to embodiments of the invention, inthe FDD duplex mode, DL transmissions 1016 and UL transmissions 1018 mayoccur substantially simultaneously, for example, at differentfrequencies (e.g., DL frequency F₁ 1024 and UL frequency F₂ 1026,respectively).

Reference is made to FIGS. 11-13, which schematically illustrate framestructures 1100, 1120, 1200, 1220, 1300, and 1320 and their respectivesub-frames, 1110, 1130, 1210, 1230, 1310, and 1330, according to variousembodiments of the present invention. In FIG. 11, TDD frame 1100 isshown with a DL/UL ratio of 4:3 and FDD frame 1120 for 5, 10 or 20 MHzchannel bandwidth with a cyclic prefix of ¼ of useful OFDM symbollength. The TDD frame 1100 may consist of seven sub-frames 1110 of sixOFDM symbols each and FDD frame 1120 may have the same configuration asthe TDD frame to maximize commonality or may consists of six sub-frames1110 of six OFDM symbols and one sub-frame 1130 of seven OFDM symbols.As an example, for an OFDM symbol duration of 114.386 microseconds (Tb)and a CP length of ¼ Tb, the length of six-symbol sub-frames 110 andseven-symbol sub-frames 1130 are 0.6857 ms and 0.80 ms, respectively. Inthis case, the transmit-to-receive transmission gap (TTG) andreceive-to-transmit transmission gap (RTG) are 139.988 microseconds and60 microseconds, respectively.

In FIG. 12, TDD frame 1200 is shown with a DL/UL ratio of 3:2 and FDDframe 1220 for 7 MHz channel bandwidth with a CP of ¼ Tb. The TDD frame1200 may consist of five six-symbol sub-frames 1210 and the FDD frame1220 may have the same structure as the TDD frame to maximizecommonality or may consist of four six-symbol sub-frames 1210 and oneseven-symbol sub-frame 1230. Assuming OFDM symbol duration of 160microseconds and a CP length of ¼ Tb, the length of six-symbol sub-frame1210 and seven-symbol sub-frame 1230 are 0.960 ms and 1.120 ms,respectively. The TTG and RTG are 140 microseconds and 60 microseconds,respectively.

In FIG. 13, TDD frame 1300 is shown with a DL/UL ratio of 4:2 and FDDframe 1320 for 8.75 MHz channel bandwidth with a CP of ¼ Tb. The TDDframe 1300 has four six-symbol sub-frames 1310 and two seven-symbolsub-frames 1330 and FDD frame 1320 has three six-symbol sub-frames 1310and three seven-symbol sub-frame 1330. Assuming OFDM symbol duration of128 microseconds and a CP length of ¼ Tb the length of six-symbolsub-frame 1310 and seven-symbol sub-frame 1330 are 0.768 ms and 0.896ms, respectively. The number of OFDM symbols in a sub-frame may berelated to, for example, the length of each OFDM symbol and/or thecyclic prefix value. However, to simplify the implementation of thesystem, it is desirable that all sub-frames within a frame have the samesize and consists of the same number of OFDM symbols. Embodiments of theinvention may be used having any suitable OFDMA numerology. It may beappreciated by those skilled in the art that although a variety ofparameters (e.g., duplex modes, cyclic prefix values, OFDMAnumerologies, etc.) may be used according to embodiments describedherein, suitable variations may be used, for example, as depicted in thevariations of FIGS. 11-13.

Reference is made to FIG. 14, which is a table of OFDMA parametersaccording to embodiments of the present invention. FIG. 14 listsparameters for a CP of ¼. The CP length of one quarter is equal to 22.85microseconds (for bandwidths of 5, 10 or 20 MHz) which corresponds to acell size of approximately 5 km. Therefore, a delay spread of up to22.85 microseconds can be mitigated.

Reference is made to FIG. 15, which is a flow chart of a methodaccording to an embodiment of the present invention.

In operation 1500, a processor in a terminal may partition each frameinto two or more sub-frames. The frames (e.g., frames 410 described inreference to FIG. 4, or other frames) may be backward compatible with areference system profile and for example, defined according to areference standard system (e.g., IEEE Std 802.16-2009 or mobile WiMAXprofiles). Thus, as compared with the frames from which sub-frames arepartitioned, the sub-frames (e.g., sub-frames 420 described in referenceto FIG. 4) may be shorter and therefore processed andtransmitted/received faster with smaller periodicity. Transmittingaccording to the sub-frame structure may provide over the aircommunications having a periodicity on the scale of several sub-framesinstead of the relatively longer periodicity of several frames.

In operation 1505, a transmitter may transmit one or more sub-framesduring a pre-designated downlink transmission (e.g., pre-designated DLtransmissions 306, described in reference to FIG. 3).

In operation 1510, the transmitter may transmit one or more sub-framesduring a pre-designated uplink transmission (e.g., pre-designated ULtransmissions 308, described in reference to FIG. 3)

In operation 1515, the transmitter may transmit one of the plurality ofsub-frames including a legacy preamble for communicating with a legacyterminal, for example, operating according to the reference systemprofile during a pre-designated legacy transmission period or zone(e.g., legacy zone 612 and/or 616, described in reference to FIG. 6).

In operation 1520, the transmitter may transmit one of the plurality ofsub-frames including a new preamble for communicating with a new (e.g.,a non-legacy) terminal, for example, operating according to an evolvedor newer version of the reference system standard, such as, the IEEE802.16m standard, during a pre-designated new (e.g., a non-legacy)transmission period or zone (e.g., new zone 614 and/or 618, described inreference to FIG. 6).

In various embodiments, the first and second signals may be transmittedin a TDD duplex mode or an FDD duplex mode. In some embodiments, whenthe signals are transmitted in a TDD duplex mode, operations 1505 and1510 may be executed over substantially different time intervals, orframe positions, such that the first and second signals may betransmitted separately. In other embodiments, when the when the signalsare transmitted in an FDD duplex mode, operations 1505 and 1510 may beexecuted in substantially overlapping time periods, such that the firstand second signals may be transmitted over substantially distinctfrequencies and/or channels.

In some embodiments, the sub-frames may be further partitioned into twoor more (e.g., six) information-carrying, multiplexing, and/or OFDMsymbols.

In some embodiments, the first and second signals may include a legacypreamble for communicating with legacy terminals operating according tothe reference system profile and a new preamble for communicating with anew (e.g., a non-legacy) terminal operating according to a second systemstandard and/or an evolved version of the reference system. In oneembodiment, each of the first and second sub-frames may bepre-designated for communicating with one of a legacy terminal, anon-legacy terminal, or both a legacy and non-legacy terminal. Forexample, one of two or more sub-frames in operation 1510 may bepre-designated for communicating with both a legacy and a non-legacyterminal.

In some embodiments, the beginning of the frames, which may bepre-designated for communicating with legacy terminals and non-legacyterminals, may be offset, for example, by a fixed number of sub-frames.

In some embodiments, a super-frame may be defined. For example, thesuper-frame may include two or more frames (e.g., the frames describedin operation 1500) that may be transmitted in succession. In oneembodiment, the new preamble may be transmitted substantially onceduring the transmission of each super-frame. In one embodiment, the newpreamble may be transmitted substantially once every frame.

According to embodiments such as that of Option I described herein, thelegacy preamble and the new preamble may be transmitted separately, forexample, at a substantially fixed distance apart along the length of theframe.

In one embodiment, a process may execute operations 1500, 1505, and 1510and need not execute operations 1515 and 1520. In another embodiment, aprocess may execute operations 1500, 1515, and 1520 and need not executeoperations 1505 and 1510. In yet another embodiment, a process mayexecute operations 1500, 1505, 1510, 1515, and 1520. The process mayexecute other sequences, orders, and/or permutations of operationsdescribed herein.

While the invention has been described with respect to a limited numberof embodiments, it will be appreciated that many variations,modifications and other applications of the invention may be made.Embodiments of the present invention may include other apparatuses forperforming the operations herein. Such apparatuses may integrate theelements discussed, or may comprise alternative components to carry outthe same purpose. It will be appreciated by skilled in the art that theappended claims are intended to cover all such modifications and changesas fall within the true spirit of the invention.

1. A method comprising: partitioning each of a plurality of frames intoa plurality of sub-frames, wherein the frames are defined according to areference system standard and wherein a cyclic prefix (CP) is onequarter of a useful symbol length; transmitting one of the plurality ofsub-frames during a pre-designated downlink transmission; andtransmitting one of the plurality of sub-frames during a pre-designateduplink transmission.
 2. The method of claim 1, wherein the partitionedframes may comprise sub-frames of equal size to simplify implementationand software and hardware processing or may comprise subframes ofunequal sizes. The number of sub-frames per frame and number of OFDMsymbols per sub-frames are determined according to the OFDMA numerologyand the number of available OFDM symbols per frame.
 3. The method ofclaim 1, further comprising partitioning each of the plurality ofsub-frames into a plurality of information-carrying symbols.
 4. Themethod of claim 3, wherein the plurality of information-carrying symbolscomprise orthogonal frequency division multiplex symbols.
 5. The methodof claim 4, wherein the number of orthogonal frequency divisionmultiplex symbols is approximately equal to six (6).
 6. The method ofclaim 1, further comprising using a time division duplex mode fortransmitting sub-frames during the pre-designated downlink and uplinktransmissions during substantially different time intervals.
 7. Themethod of claim 1, further comprising using a frequency division duplexmode for transmitting signals in sub-frames over substantially differentfrequencies.
 8. A method comprising: partitioning each of a plurality offrames into a plurality of sub-frames, wherein the frames are definedaccording to a reference system standard and wherein a cyclic prefix(CP) is one quarter of a useful symbol length; transmitting one or moreof the plurality of sub-frames for a non-relay transmission includingtransmitting a (DL: BS->MS/RS) sub-frame during a pre-designateddownlink transmission and a (UL:MS/RS->BS) sub-frame during apre-designated uplink transmission; and transmitting one or more of theplurality of sub-frames for a relay transmission including transmittinga (DL:RS->MS) sub-frame during a pre-designated downlink transmissionand a (UL:MS->RS) sub-frame during a pre-designated uplink transmission.9. The method of claim 8, further comprising supporting a two-hop relaytransmission.
 10. The method of claim 9, further comprising supporting atwo-hop relay with optimized latency
 11. The method of claim 8, furthercomprising further partitioning each of a plurality of frames bypartitioning even-numbered hop zones into (DL: BS->MS, BS->odd RS, evenRS->odd RS) zones during a pre-designated downlink transmission and (UL:MS->BS, odd RS->BS, odd RS->even RS) during a pre-designated uplinktransmission and odd-numbered hop zone into (DL: odd RS->even RS, oddRS->MS) zones during a pre-designated downlink transmission and (UL:MS->odd RS, even RS->odd RS) during a pre-designated uplinktransmission.
 12. The method of claim 11, further comprisingtransmitting using a multi-hop relay transmission.
 13. The method ofclaim 8, further comprising using a transparent relay, where the RS doesnot transmit a preamble, a broadcast channel, and a control channel. 14.The method of claim 8, further comprising using a non-transparent relay,where the RS transmits a preamble, a broadcast channel, and a controlchannel.
 15. A system comprising: a processor to partition each of aplurality of frames into a plurality of sub-frames, wherein the framesare defined according to reference system standard and wherein a cyclicprefix (CP) is one quarter of a useful symbol length; and a transmitterto transmit one of the plurality of sub-frames during a pre-designateddownlink transmission and one of the plurality of sub-frames during apre-designated uplink transmission.
 16. The system of claim 15, whereinthe processor is to partition the sub-frames to have a length selectedfor achieving a turn-around time that is below a predetermined targetvalue.
 17. The system of claim 15, wherein the processor is to partitioneach of the plurality of sub-frames into a plurality ofinformation-carrying symbols.
 18. The system of claim 17, wherein theplurality of information-carrying symbols comprise orthogonal frequencydivision multiplex symbols.
 19. The system of claim 15, wherein thetransmitter is to transmit during substantially different time intervalsusing a time division duplex mode.
 20. The system of claim 15, whereinthe transmitter is to transmit over substantially different frequenciesusing a frequency division duplex mode.